EVALUATION OF INDOPHENOL DERIVATIVES AS REAGENTS FOR DEMONSTRATING CYTOCHROME OXIDASE IN TISSUE SECTIONS

Abstract

Seven redox dyes were investigated as possible histochemical indicators of cytochrome oxidase activity. All failed to meet one prime requisite, namely, that the oxidized product remain at the site of enzymatic action. The "color fading" phenomenon was studied. This effect was one in which sections and homogenates became colored as a result of oxidase activity and then faded during further incubation. Evidence was provided that this reaction occurred as a result of endogenous dehydrogenase activity, mainly succinic dehydrogenase. The decoloration in solution could be prevented by N-ethyl maleimide, without inhibiting cytochrome oxidase.